Re: [RFC PATCH] configure: deprecate 32 bit build hosts

[Alex Bennée]

Thomas Huth <address@hidden> writes:

> On 26/09/2019 15.46, Christian Borntraeger wrote:
>>
>>
>> On 26.09.19 14:58, Daniel P. Berrangé wrote:
>>> On Thu, Sep 26, 2019 at 08:50:36AM +0100, Peter Maydell wrote:
>>>> On Thu, 26 Sep 2019 at 00:31, Alex Bennée <address@hidden> wrote:
>>>>>
>>>>> The 32 bit hosts are already a second class citizen especially with
>>>>> support for running 64 bit guests under TCG. We are also limited by
>>>>> testing as actual working 32 bit machines are getting quite rare in
>>>>> developers personal menageries. For TCG supporting newer types like
>>>>> Int128 is a lot harder with 32 bit calling conventions compared to
>>>>> their larger bit sized cousins. Fundamentally address space is the
>>>>> most useful thing for the translator to have even for a 32 bit guest a
>>>>> 32 bit host is quite constrained.
>>>>>
>>>>> As far as I'm aware 32 bit KVM users are even less numerous. Even
>>>>> ILP32 doesn't make much sense given the address space QEMU needs to
>>>>> manage.
>>>>
>>>> For KVM we should wait until the kernel chooses to drop support,
>>>> I think.
>>>
>>> What if the kernel is waiting for QEMU to drop support too ;-P
>>
>> For what its worth on kvm/s390 we never cared about implementing
>> 32 bit.
>
> Looking at tcg/s390/tcg-target.inc.c :
>
> ...
> /* We only support generating code for 64-bit mode.  */
> #if TCG_TARGET_REG_BITS != 64
> #error "unsupported code generation mode"
> #endif
> ...
>
> ... it seems to me that TCG does not support 32-bit on s390 either. I
> think we can remove s390 (32-bit) from the list completely?

It's the same for riscv32 I think.

>
>  Thomas


--
Alex Bennée